Bloemfontein - The Democratic Alliance in the Free State on Wednesday called for an urgent clean-up operation after dead fish were found washed up on the edge of the Loch Lomond lake outside Bethlehem.

Residents from adjacent Bohlokong were seen harvesting the dead fish in large numbers, said leader of the official opposition Roy Jankielsohn.

Jankielsohn said the DA was concerned at the "slow" response by the Dihlabeng Local Municipality, which had not yet begun a clean-up operation.

"The current disaster will totally destroy this unique ecosystem and can only be rehabilitated if the sources of the problem are dealt with effectively," he said.

Jankielsohn said they suspected that sustained pollution caused by raw sewage seeping from a nearby sewerage plant and industrial pollutants could be the cause.

Residents warned

"A clean-up operation to contain the disaster must be launched without any further delay followed by a rehabilitation programme to ensure the area is safe for use by the local community."

He also warned that the polluted water from the lake might end up in the Liebenbergsvlei River and pollute the water in the Lesotho Highland Scheme, which is crucial to South Africa's water supply.

The Free State Department of Health on Tuesday warned residents of Bethlehem not to eat any fish from the lake.

"The people of Bethlehem should desist from eating the fish caught in this lake and any other food items that are harvested from non-certified and approved food outlets," said department spokesperson Mondli Mvambi.

Environmental officers had been sent to investigate. The cause of the fish deaths was unknown.

Mvambi said the department was worried about residents who were seen collecting the fish.